An important application of pluripotent cells is their use in cell therapy. Pluripotent stem cells include, but are not limited to, human embryonic stem (hES) cells, human embryonic germ (hEG) cells. Still other types of pluripotent cells exist, for example, dedifferentiated mouse and human stem cells, i.e. differentiated somatic adult cells are dedifferentiated to become pluripotent-like stem cells. These dedifferentiated cells induced to establish cells having pluripotency and growth ability similar to those of ES cells are also called “induced pluripotent stem (iPS) cells”, “embryonic stem cell-like cells”, “ES-like cells”, or equivalents thereof. Such cells are potentially viable alternative pluripotent cells. The therapeutic application of iPS cells will require demonstrating that these cells are stable and show an appropriate safety profile in preclinical studies to treat diabetes and other diseases. Reprogramming of differentiated human somatic cells into a pluripotent state allows for patient- and disease-specific stem cells. See Takahashi, K. et al. Cell, 1-12, 2007 and Ju, J. et al. Science 2007. Takahashi et al. and Ju et al. each introduced four genes into adult and fetal/newborn fibroblasts to generate the iPS cells: Oct4, Sox2, Klf4 and c-myc by Takahashi et al.; Oct4, Sox2, Nanog and Lin28 by Ju et al. In either case, iPS cells had some characteristics of hES cells including, hES cell morphology, marker expression, prolonged proliferation, normal karyotype, and pluripotency.
Although, iPS cells may provide a cell therapy-based regenerative medicine without the associated ethical controversy, the differentiation properties of iPS cells, for example, differentiation potential and efficiency of the differentiation in vitro, are still unclear, and a directed differentiation method for iPS cells has not been demonstrated. Hence, there is a need to determine and demonstrate detailed differentiation properties and the directional differentiation efficiencies of iPS cells.